Method for processing contaminated wastewater from the preparation of isophorone, isophoronenitrile and isophoronediamine

ABSTRACT

Contaminated wastewater from the preparation of isophorone, isophoronenitrile and isophoronediamine is treated by A) 1. treating the wastewater from the preparation of isophoronenitrile from the reaction of isophorone with hydrogen cyanide by alkaline hydrolysis of isophoronenitrile to isophorone, and the salts of hydrogen cyanide within a pH range of 12.0 to 13.7 and at temperatures of 60 to 200° C. and 2. processing the wastewater from A) 1. by an oxidation, or B) treating the wastewater from the preparation of isophoronenitrile from the reaction of isophorone with hydrogen cyanide by an oxidation, or C) processing the wastewater from A) 1. and the wastewater from the preparation of isophorone and/or the wastewater from the preparation of isophoronediamine by an oxidation.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a method for processing contaminated wastewaterfrom the preparation of isophorone, isophoronenitrile andisophoronediamine.

Discussion of the Background RELATED ART

WO 2012/076317 (PCT/EP2011/070442) discloses a process for preparing3-aminomethyl-3,5,5-trimethylcyclohexylamine.

There is a detailed description of a three-stage process for preparing3-aminomethyl-3,5,5-trimethylcyclohexylamine, referred to hereinafter asisophoronediamine or IPDA for short, by

I. preparation of isophorone by catalyzed aldol condensations withacetone as reactant:

II. reaction of isophorone with hydrogen cyanide to formisophoronenitrile (IPN, 3-cyano-3,5,5-trimethylcyclohexanone):

III. catalytic hydrogenation and/or catalytic reductive amination (alsoreferred to as aminating hydrogenation) of3-cyano-3,5,5-trimethylcyclohexanone, referred to hereinafter asisophoronenitrile or IPN for short, to give isophoronediamine.

At the end of all three stages, a wastewater comprising thecorresponding end products and also starting materials is obtained.

SUMMARY OF THE INVENTION

A problem addressed by the present invention was that of finding amethod for processing the wastewater contaminated with isophorone,isophoronenitrile, isophoronediamine, hydrogen cyanide or salts ofhydrogen cyanide, and possibly further substances, wherein the treatedwastewater obtained thereby can be sent to a biological wastewatertreatment. Isophoronenitrile in particular exhibits poorbiodegradability. By the degradation tests according to DIN EN ISO 9888,the isophorone wastewater was classified as non-biodegradable with a CODreduction of <15%.

It has been found that a method according to this invention solves theproblem.

In one embodiment, the present invention provides a method forprocessing contaminated wastewater from the preparation of isophorone,isophoronenitrile and/or isophoronediamine, the method comprising:

A)

1. treating the wastewater from the preparation of isophoronenitrilefrom the reaction of isophorone with hydrogen cyanide by alkalinehydrolysis of isophoronenitrile to isophorone, and the salts of hydrogencyanide within a pH range of 12.0 to 13.7 and at temperatures of 60 to200° C.,

and

2. processing the wastewater from A) 1. by an oxidation,

or

B)

treating the wastewater from the preparation of isophoronenitrile fromthe reaction of isophorone with hydrogen cyanide by an oxidation,

or

C)

processing the wastewater from A) 1. and the wastewater from thepreparation of isophorone and/or the wastewater from the preparation ofisophoronediamine by an oxidation.

In another embodiment, the present invention provides a method forprocessing contaminated wastewater from the preparation of isophorone,isophoronenitrile and/or isophoronediamine, comprising a preparation of3-aminomethyl-3,5,5-trimethylcyclohexylamine which is carried out bysteps I.-III.:

I. preparing isophorone by catalyzed aldol condensation with acetone asreactant,

II. reacting isophorone with hydrogen cyanide to form3-cyano-3,5,5-trimethylcyclohexanone,

III. catalytically hydrogenating and/or catalytically reductivelyaminating 3-cyano-3,5,5-trimethylcyclohexanone to isophoronediamine,

by a method comprising

A)

1. treating the wastewater from the preparation of isophoronenitrilefrom the reaction of isophorone with hydrogen cyanide from step II byalkaline hydrolysis of isophoronenitrile to isophorone, and the salts ofhydrogen cyanide within a pH range from 12.5 to 13.7 at temperatures of60 to 200° C.,

and

2. processing the wastewater from A) 1. by oxidation,

or

B)

treating the wastewater from the preparation of isophoronenitrile II.from the reaction of isophorone with hydrogen cyanide by oxidation,

or

C)

processing the wastewater from A) 1. and the wastewater from thepreparation of isophorone from step I and/or the wastewater from thepreparation of isophoronediamine from step III by an oxidation.

DETAILED DESCRIPTION OF THE INVENTION

All ranges herein below include all values and subvalues between thelower and higher limit of the range.

The invention provides a method for processing contaminated wastewaterfrom the preparation of isophorone, isophoronenitrile andisophoronediamine,

said wastewater comprising especially isophorone, isophoronenitrile,isophoronediamine, hydrogen cyanide or salts of hydrogen cyanide,ammonium salts, alone or in mixtures.

by

A)

-   -   1. treating the wastewater from the preparation of        isophoronenitrile from the reaction of isophorone with hydrogen        cyanide by alkaline hydrolysis of isophoronenitrile to        isophorone, and the salts of hydrogen cyanide within a pH range        from 12.5 to 13.7 at temperatures of 60 to 200° C., preferably        at 80 to 180° C. and more preferably at 95 to 120° C.,

and

-   -   2. processing the wastewater from 1. by an oxidation,

or

B)

treating the wastewater from the preparation of isophoronenitrile fromthe reaction of isophorone with hydrogen cyanide by oxidation,

or

C)

processing the wastewater from 1. and the wastewater from thepreparation of isophorone and/or the wastewater from the preparation ofisophoronediamine by an oxidation.

The invention preferably provides a method for processing contaminatedwastewater from the preparation of isophorone, isophoronenitrile and/orisophoronediamine, wherein the preparation of3-aminomethyl-3,5,5-trimethylcyclohexylamine, called isophoronediamineor IPDA for short hereinafter, is carried out by steps I.-III.:

-   -   I. preparing isophorone by catalyzed aldol condensation with        acetone as reactant,    -   II. reacting isophorone with hydrogen cyanide to form        3-cyano-3,5,5-trimethylcyclohexanone (isophoronenitrile),    -   III. catalytically hydrogenating and/or catalytically        reductively aminating (also referred to as aminating        hydrogenation) 3-cyano-3,5,5-trimethylcyclohexanone        (isophoronenitrile) to isophoronediamine,

and

A)

-   -   1. treating the wastewater from the preparation of        isophoronenitrile from the reaction of isophorone with hydrogen        cyanide from step II by alkaline hydrolysis of isophoronenitrile        to isophorone, and the salts of hydrogen cyanide within a pH        range from 12.5 to 13.7 at temperatures of 60 to 200° C.,        preferably at 80 to 180° C. and more preferably at 95 to 120°        C.,    -   and    -   2. processing the wastewater from 1. by oxidation,

or

B)

treating the wastewater from the preparation of isophoronenitrile II.from the reaction of isophorone with hydrogen cyanide by oxidation,

or

C)

processing the wastewater from A) 1. and the wastewater from thepreparation of isophorone from step I and/or the wastewater from thepreparation of isophoronediamine from step III by an oxidation.

Description of the Alkaline Hydrolysis 1.

The wastewater obtained in the preparation of isophoronenitrile, havinga pH of 1 to 2, contains, as well as other components from the process,˜2000 ppm of isophoronenitrile.

The isophoronenitrile present has to be removed, since the wastewatermust not be introduced into the biological wastewater treatment plant.

The problem addressed was that of significantly reducing theisophoronenitrile content in order to be able to send the wastewaterdirectly to the biological wastewater treatment plant.

Alkaline hydrolysis of nitriles to the corresponding carboxylic acids isknown from literature (Grundlagen der Organischen Chemie [Fundamentalsof Organic Chemistry], page 584, Joachim Buddrus).

It has been found, surprisingly, in a new finding, thatisophoronenitrile is cleaved to isophorone within a particulartemperature range and a particular pH range.

The alkaline hydrolysis, in a pH range from 12.5 to 13.7, ofisophoronenitrile is conducted at temperatures of 60) to 200° C.,preferably at 80 to 180° C. and more preferably at 95 to 120° C.

After the alkaline hydrolysis, an isophoronenitrile content in thebottoms of the hydrolysis column of not more than 5 mg/l is attained.The isophorone formed is drawn off at the top of the hydrolysis columnby distillation, together with other low boilers, for example acetone,and is fed back to the upstream process.

Suitable bases in this context are all inorganic and organic bases,especially those of the metals of the first and second main groups ofthe Periodic Table. Preference is given to using aqueous alkali,especially aqueous sodium hydroxide solution. The pH during thehydrolysis vanes from 12.5 to 13.7, preferably from 13.0 to 13.5. Theresidence time in the bottom of the hydrolysis column depends on theconcentration of isophoronenitrile. In general, it is 10 to 30 minutes.

The treated IPN had very good biodegradability with an adaptation timeof >30 days. A COD reduction of >90% was attained after about 55 days.The strippable components were ≤10% of the total COD reduction. Thus,there are no hazardous waste air emissions during the ventilation phasein the biological wastewater treatment.

Description of the Oxidation

The method is characterized in that the wastewater from 1. or thewastewater from the preparation of isophoronenitrile from the reactionof isophorone with hydrogen cyanide (step B) or the wastewater from 1.and the wastewater from the preparation of isophorone and/or thewastewater from the preparation of isophoronediamine (step C) areprocessed by an oxidation in such a way that the COD (COD=chemicaloxygen demand, according to DIN 38409 H41) is significantly reduced,hydrogen cyanide or salts thereof present are oxidized to form carbondioxide, ammonium compounds can be eliminated, and the resultingwastewater may be introduced into a biological wastewater treatmentplant for further treatment. The combination of method steps enablesfurther cleaning than only by one step, for example a biologicalcleaning operation itself. Preferably, a significant reduction in COD ofat least 50%, more preferably of 70%, is achieved by the oxidation.

The oxidation step is characterized in that the oxidizing agents usableare substances such as hydrogen peroxide, activated hydrogen peroxide(activated by iron, UV or ozone). Caroat, but preferably sodiumhypochlorite solution or hypochlorite produced in situ by chlorineinjection. In addition, oxidation can be effected by means of chlorinedioxide.

The oxidation can be executed within a wide pH range, preferably betweenpH 11 and pH 5, beginning with a higher pH and then moving to lower pHvalues, during the oxidation process, for example through a cascade of 3reactors in which different pH values are then established.

The oxidation method is additionally characterized in that it can beconducted at ambient temperatures or else at elevated temperatures toincrease the reaction rate. The preferred temperature range during theoxidation is between 10 and 50° C.

The invention also provides a method, characterized in that

the wastewater, subsequent to the method described above, is subjectedto a biological wastewater treatment.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only, and are not intended to belimiting unless otherwise specified.

The invention is elucidated in detail by the examples which follow.

EXAMPLES Examples for A) 1 Example 1

Batch Hydrolysis

In a hydrolysis column, a synthetic wastewater comprising 12 g ofisophoronenitrile dissolved in 1500 g of water was adjusted to a pH of13 with 7 g of NaOH and kept under reflux at 100° C. for 2 hours. Thesubsequent GC analysis of the bottom product showed an isophoronenitrilecontent of 2 mg/l.

During the hydrolysis, 100 ml were distilled off and the GC analysis ofthe distillate showed an isophorone content of 1385 mg/l.

The wastewater (bottom product) thus obtained was processed without anyproblem in the downstream biological wastewater treatment.

Example 2 Continuous Hydrolysis at pH 13.7

750 ml/h of wastewater from a process plant having an isophoronenitrilecontent of 1885 mg/l were introduced continuously into the bottom of thehydrolysis column.

By means of closed-loop control of the bottoms level, a residence timein the bottom of 1.5 hours was established, and the pH in the bottomswas adjusted to pH 13.7 by metered addition of 20% NaOH.

The temperature in the bottom of the column was 102° C.

Over a period of 6.5 hours, 4875 ml of process wastewater were thus runthrough the hydrolysis column. The GC analysis of the outgoing bottomproduct still showed a residual isophoronenitrile content of 1 mg/l andan isophorone content of 83 mg/l.

Within the 6.5 hours, 340 ml of distillate were drawn off at the top ofthe column. The GC analysis showed an isophorone content of 14 900 mg/l.

Mass Balance:

for every 1000 mg of IPN, 836 mg of IP can form

IPN input: 4.8751*1885 mg/l=9189 mg IPN; =>7682 mg IP

Discharge of IP

1. In the distillate: 340 ml*14 900 mg/l/1000=5066 mg IP

2. In the bottoms: 4535 ml*83 mg/l/1000=376 mg IP

70.8% of the amount of isophorone theoretically possible was detectedanalytically.

Example 3

Continuous Hydrolysis at pH 11

750 ml/h of wastewater from a process plant having an isophoronenitrilecontent of 1885 mg/l were introduced continuously into the bottom of thehydrolysis column.

By means of closed-loop control of the bottoms level, a residence timein the bottom of 1.5 hours was established, and the pH in the bottomswas adjusted to pH 11 by metered addition of 20% NaOH.

The temperature in the bottom of the column was 102° C.

Over a period of 6.0 hours, 4500 ml of process wastewater were thus runthrough the hydrolysis column. The GC analysis of the outgoing bottomproduct still showed a residual isophoronenitrile content of 620 mg/land an isophorone content of 53 mg/.

Example 4

Continuous Hydrolysis at pH 9

750 ml/h of wastewater from a process plant having an isophoronenitrilecontent of 1885 mg/l were introduced continuously into the bottom of thehydrolysis column.

By means of closed-loop control of the bottoms level, a residence timein the bottom of 1.5 hours was established, and the pH in the bottomswas adjusted to pH 9 by metered addition of 20% NaOH.

The temperature in the bottom of the column was 102° C.

Over a period of 5.0 hours, 3750 ml of process wastewater were thus runthrough the hydrolysis column. The GC analysis of the outgoing bottomproduct still showed a residual isophoronenitrile content of 1284 mg/land an isophorone content of 15 mg/l.

GC Analysis:

GC settings Agilent 6890N Chromeleon software EXTRELUT Separationcolumns HP-5 Fused silica capillary: 30 m; 0.25 mm ID; film thickness0.25 μm Temperatures Injector 250° C. Detector (FID) 250° C. Oven 80° C.// 4 min // 7° C./min // 180° C. // 17 min Carrier gas helium columnpressure 17 psi Split 16 ml/min Septum purge 2.0 ml/min Combustion gases35 ml/min hydrogen 300 ml/min air 20 m/min make-up gasInstruments/reagents Extrelut NT1 columns from Merck dil. Standardsolution 3.0 mg n-C₁₄H₃₀ in 6 ml CCl₄ Sample preparation 100 ml ofsample are adjusted to pH 2 with HCl solution (dilution factor). TheExtrelut NT1 column is placed onto the analytical balance, 1 ml of theacidified sample is applied and the system is weighed. A contact time of10 min is allowed and elution is effected with 6 ml of standardsolution. The eluate is collected in a 10 ml measuring cylinder, theamount of eluate is read off and 2 μl are injected into the GC.Injection volume 2.0 μl sample solution Evaluation Internal standardmethod Result = mg C₁₄ (=ml eluate × 0.5) × Ai × RRF × dil. factor ×10⁶/(weight in mg × Astd)

Examples of Oxidation

Example 5

A wastewater mixture from the production of isophorone,isophoronenitrile, isophoronediamine, characterized by a CODconcentration of 3170 mg/l, was heated to 40° C. and reacted with anabout 10% sodium hypochlorite solution. The pH in the mixture oncommencement of reaction was 12.9; the temperature was 40° C. Over thecourse of about 3 hours, the pH fell to 9.3 and was then lowered to a pHof 7.7 with sulphuric acid. After a further hour of reaction time, thereaction was stopped by destroying the remaining residue of sodiumhypochlorite with sodium sulphite. The COD concentration measured afterthe reaction, measured by Hach Lange cuvette tests, in this experimentwas 1240 mg/l, corresponding to a COD elimination rate of 60.8%. In asubsequent static biological degradation test for simulation of abiological wastewater treatment plant, an improved COD degradation of46% was determined, compared to 36% from the untreated wastewatermixture. With regard to the NH4-N (ammonium-nitrogen) content, it waspossible to reduce this in the course of the oxidative treatment to aconcentration of <5 mg/l NH4-N. Measurement by Hach Lange cuvette tests.

For wastewater introductions into water bodies, legally stipulatedlimits for nitrogen compounds are fixed.

The target for the limit for NH4N in the wastewater from the treatmentplant, in accordance with the invention, is less than or equal to 10mg/l. Measurement by Hach Lange cuvette tests.

During the biological wastewater treatment, NH4-N is then converted withoxygen supply via NO2-N to NO3-N.

Example 6

A wastewater from an isophoronenitrile production, characterized by aCOD content of 4900 mg/l, was heated to about 40° C. and reacted with anabout 10% sodium hypochlorite solution. The pH in the mixture oncommencement of reaction was 11.3; the temperature was 40° C. After onehour and after two hours of reaction time, further hypochlorite solutionwas metered in and the pH, if required, was corrected in the directionof pH˜10 with NaOH. After about 3 hours of reaction time, the pH waslowered to a pH of 7.3 with sulphuric acid. Over the course of a furtherhour of reaction time, the pH fell to about 6.7. Subsequently, thereaction was stopped by destroying the remaining residue of sodiumhypochlorite with sodium sulphite. The COD concentration measured afterthe reaction, measured by Hach Lange cuvette tests, in this experimentwas 1300 mg/l, corresponding to a COD elimination rate of 73%. In asubsequent static biological degradation test for simulation of abiological wastewater treatment plant, an improved COD degradation of50% was determined, compared to 14% from the untreated wastewater.

With regard to the NH4-N content, it was possible to reduce this in thecourse of the oxidative treatment to a concentration of <5 mg/l NH4-N.Measurement by Hach Lange cuvette tests.

Test Method:

Hach Lange cuvette test, measured to ISO 6060-1989, DIN 38409-H41-H44.

European patent application EP14195357 filed Nov. 28, 2014, isincorporated herein by reference.

Numerous modifications and variations on the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1: A method for processing contaminated wastewater from a preparation ofisophorone, isophoronenitrile and/or isophoronediamine, the methodcomprising: B) treating, by oxidation, wastewater from the preparationof isophoronenitrile by reaction of isophorone with hydrogen cyanide, orC) processing, by oxidation, wastewater from a stage A) 1) andwastewater from the preparation of isophorone and/or the wastewater fromthe preparation of isophoronediamine, wherein stage A) 1) comprisestreating the wastewater from the preparation of isophoronenitrile fromthe reaction of isophorone with hydrogen cyanide by alkaline hydrolysisof isophoronenitrile to isophorone, and the salts of hydrogen cyanidewithin a pH range of 12.0 to 13.7 and at temperatures of 60 to 200° C.2: A method for processing contaminated wastewater from a preparation ofisophorone, isophoronenitrile and/or isophoronediamine, the methodcomprising: a preparation of3-aminomethyl-3,5,5-trimethylcyclohexylamine which is carried out byI-III: I preparing isophorone by catalyzed aldol condensation withacetone as reactant, II reacting isophorone with hydrogen cyanide toform isophoronenitrile, III catalytically hydrogenating and/orcatalytically reductively aminating isophoronenitrile toisophoronediamine, the method further comprising B) or C) B) treating,by oxidation, wastewater from the preparation of isophoronenitrile fromstage II from the reaction of isophorone with hydrogen cyanide or C)processing, by oxidation, wastewater from a stage A) 1) and thewastewater from the preparation of isophorone from stage I or thewastewater from the preparation of isophoronediamine from stage III,wherein stage A) 1) comprises treating the wastewater from thepreparation of isophoronenitrile from the reaction of isophorone withhydrogen cyanide from stage II by alkaline hydrolysis ofisophoronenitrile to isophorone, and the salts of hydrogen cyanidewithin a pH range from 12.5 to 13.7 at temperatures of 60 to 200° C. 3:The method according to claim 1, wherein the contaminated wastewatercomprises isophorone, isophoronenitrile, isophoronediamine, hydrogencyanide or salts of hydrogen cyanide, ammonium salts, alone or inmixtures. 4: The method according to claim 1, wherein, in stage A) 1),the alkaline hydrolysis is effected at temperatures of 80 to 180° C. 5:The method according to claim 1, wherein, after the alkaline hydrolysisin stage A) 1), an isophoronenitrile content in the bottoms of thehydrolysis column of not more than 5 mg/l is attained. 6: The methodaccording to claim 1, wherein, in stage A) 1), the isophorone formed isdrawn off at the top of the hydrolysis column by distillation, togetherwith other low boilers, and is fed back upstream to the method. 7: Themethod according to claim 1, wherein, in stage A) 1), a base of a metalof the first and/or second main groups of the Periodic Table is used. 8:The method according to claim 1, wherein the oxidation of B) or C)achieves a reduction in COD, of at least 50%. 9: The method according toclaim 1, wherein at least one oxidizing agent selected from the groupconsisting of hydrogen peroxide; activated hydrogen peroxide which isactivated by iron, UV or ozone; Caroat; sodium hypochlorite solution;hypochlorite produced in situ by chlorine injection; and chlorinedioxide, is used for the oxidation. 10: The method according to claim 1,wherein the oxidation is conducted within a pH range between pH 11 andpH
 5. 11: The method according to claim 1, wherein the oxidation isconducted within a pH range between pH 11 and pH 5 in a cascadecomprising 3 reactors in which the different pH values are established.12: The method according to claim 1, wherein the oxidation is conductedwithin a temperature range between 10 and 50° C. 13: The methodaccording to claim 1, further comprising: subjecting the wastewatersubsequently to a biological wastewater treatment.
 14. (canceled) 15:The method according to claim 1, wherein B) is performed. 16: The methodaccording to claim 1, wherein C) is performed.
 17. (canceled) 18: Themethod according to claim 2, wherein B) is performed. 19: The methodaccording to claim 2, wherein C) is performed. 20: The method accordingto claim 2, wherein the contaminated wastewater comprises isophorone,isophoronenitrile, isophoronediamine, hydrogen cyanide or salts ofhydrogen cyanide, ammonium salts, alone or in mixtures. 21: The methodaccording to claim 2, wherein, in stage A) 1), the alkaline hydrolysisis effected at temperatures of 80 to 180° C. 22: The method according toclaim 2, wherein, after the alkaline hydrolysis in stage A) 1, anisophoronenitrile content in the bottoms of the hydrolysis column of notmore than 5 mg/l is attained. 23: The method according to claim 2,wherein, in stage A) 1), the isophorone formed is drawn off at the topof the hydrolysis column by distillation, together with other lowboilers, and is fed back upstream to the method. 24: The methodaccording to claim 2, wherein, in stage A) 1), a base of a metal of thefirst and/or second main groups of the Periodic Table is used. 25: Themethod according to claim 2, wherein the oxidation of B) or C) achievesa reduction in COD, of at least 50%. 26: The method according to claim2, wherein at least one oxidizing agent selected from the groupconsisting of hydrogen peroxide; activated hydrogen peroxide which isactivated by iron, UV or ozone: Caroat; sodium hypochlorite solution;hypochlorite produced in situ by chlorine injection; and chlorinedioxide, is used for the oxidation. 27: The method according to claim 2,wherein the oxidation is conducted within a pH range between pH 11 andpH
 5. 28: The method according to claim 2, wherein the oxidation isconducted within a pH range between pH 11 and pH 5 in a cascadecomprising 3 reactors in which the different pH values are established.29: The method according to claim 2, wherein the oxidation is conductedwithin a temperature range between 10 and 50° C. 30: The methodaccording to claim 2, further comprising: subjecting the wastewatersubsequently to a biological wastewater treatment.